1. Field of the Invention
The present invention relates to a magnetic head for perpendicular magnetic recording that is used for recording data on a recording medium by means of a perpendicular magnetic recording system, a method of manufacturing the same, and a head assembly and a magnetic recording device each of which includes the magnetic head for perpendicular magnetic recording.
2. Description of the Related Art
Recently, magnetic recording devices such as a magnetic disk drive have been improved in recording density, and magnetic heads and magnetic recording media of improved performance have been demanded accordingly. The recording systems of magnetic recording devices include a longitudinal magnetic recording system wherein signals are magnetized in a direction along the plane of the recording medium (the longitudinal direction) and a perpendicular magnetic recording system wherein signals are magnetized in a direction perpendicular to the plane of the recording medium. As compared with the longitudinal magnetic recording system, the perpendicular magnetic recording system is harder to be affected by thermal fluctuation of the recording medium and capable of providing higher linear recording density.
Magnetic heads for perpendicular magnetic recording typically have, as do magnetic heads for longitudinal magnetic recording, a structure in which a reproducing head including a magnetoresistive element (hereinafter, also referred to as an MR element) for reading and a recording head including an induction-type electromagnetic transducer for writing are stacked on a substrate. The recording head includes a main magnetic pole that produces a magnetic field in the direction perpendicular to the plane of the recording medium. The main magnetic pole includes, for example, a track width defining portion having an end located in a medium facing surface that faces the recording medium, and a wide portion that is coupled to the other end of the track width defining portion and is greater in width than the track width defining portion. The track width defining portion has a nearly uniform width.
What is required of the recording head for achieving higher recording density is reduction in track width and improvement in recording characteristics, in particular. Reducing the track width leads to degradation of the recording characteristics, such as overwrite property which is a parameter indicating an overwriting capability. A further improvement in recording characteristics is therefore required as the track width is reduced.
A magnetic head for use in a magnetic disk drive is typically provided in a slider. The slider has the medium facing surface mentioned above. The medium facing surface has an air-inflow-side end and an air-outflow-side end. The slider is configured to slightly fly over the surface of the recording medium by means of an airflow that comes from the air-inflow-side end into the space between the medium facing surface and the recording medium. The magnetic head is typically disposed near the air-outflow-side end of the medium facing surface of the slider. In a magnetic disk drive, positioning of the magnetic head is performed by a rotary actuator, for example. In this case, the magnetic head moves over the recording medium along a circular orbit about the center of rotation of the rotary actuator. In such a magnetic disk drive, a tilt of the magnetic head with respect to the tangent of the circular track, which is called a skew, occurs according to the position of the magnetic head across the tracks.
In a magnetic disk drive of the perpendicular magnetic recording system, in particular, which exhibits a better capability of writing on a recording medium compared with the longitudinal magnetic recording system, the skew mentioned above can cause a phenomenon called adjacent track erase or wide-range adjacent track erase, that is, the phenomenon that signals already recorded on one or more tracks that are adjacent to a track targeted for recording are erased or attenuated when recording a signal on the track targeted for recording. Suppression of the adjacent track erase or wide-range adjacent track erase is required in order to achieve a higher recording density.
In order for a magnetic head for perpendicular magnetic recording to achieve reduction in track width and improvement in overwrite property at the same time, it is effective to increase the thickness of the main magnetic pole so as to increase the area of the cross section of the main magnetic pole perpendicular to the direction of flow of the magnetic flux. If the entire main magnetic pole is increased in thickness, however, the adjacent track erase or wide-range adjacent track erase becomes more likely to occur. This makes it difficult to increase the recording density.
U.S. Patent Application Publication No. 2008/0239567 A1 and U.S. Patent Application Publication No. 2009/0002884 A1 each describe a main magnetic pole that is configured to have a first part that extends from the medium facing surface to a point at a predetermined distance from the medium facing surface, and a second part that is other than the first part. The main magnetic pole changes in at least either one of width and thickness at the boundary between the first part and the second part so that the second part has a larger cross-sectional area than that of the first part. The main magnetic pole of such a configuration allows the suppression of adjacent track erase or wide-range adjacent track erase, and at the same time allows the improvement of overwrite property.
In general, there is a trade-off between the suppression of adjacent track erase or wide-range adjacent track erase and the improvement of overwrite property. If the main magnetic pole is configured to have the foregoing first and second parts, the shape of the main magnetic pole affects both the adjacent track erase or wide-range adjacent track erase and the overwrite property. More specifically, if the cross-sectional area of the second part increases too much as compared with that of the first part, the overwrite property can be improved but the adjacent track erase or wide-range adjacent track erase is more likely to occur. If, on the other hand, the cross-sectional area of the second part increases too little as compared with that of the first part, the adjacent track erase or wide-range adjacent track erase can be suppressed but the overwrite property cannot be improved. To achieve the suppression of adjacent track erase or wide-range adjacent track erase and the improvement of overwrite property at the same time, it is therefore necessary to precisely control the shape of the main magnetic pole.
It has conventionally been difficult, however, to precisely control the shape of the main magnetic pole when the main magnetic pole is configured to have the foregoing first and second parts.